Electronic counting fuze

ABSTRACT

A counting fuze for a land mine having a detonator, comprising: an electrical source unit providing an output only when subjected to pressure; a charge storage means, said storage means receiving a charge in pulse form from said electrical source unit upon each subjection of said source unit to pressure; and electronic gating means, said gating means connected intermediately between said storage means and said detonator, whereby said detonator will be activated after successive applications of pressure to said electrical source unit.

United States Patent [191 Gardner [4 Oct. 21, 1975 ELECTRONIC COUNTING FUZE Carl J. Gardner, Wharton, NJ.

[73] Assignee: The United States of America as represented by the Secretary of the Army, Washington, DC.

22 Filed: Feb. 3, 1971 21 Appl. No.: 112,422

[44] Published under the Trial Voluntary Protest Program on January 28, 1975 as document no.

[75] Inventor:

[52] US. Cl..... 102/70.2 R; 102/19.2; 102/702 GA [51] Int. Cl. F42C 11/00 [58] Field of Search 102/702 1, 70.2 A, 70.2 GA, 102/70.2 R, 19.2

[56] References Cited UNITED STATES PATENTS 3,009,419 11/1961 Clay, Jr. et a1. 102/702 1 3,018,732 1/1962 Tognola 102/702 1 3,054,352 9/1962 Perdreaux, Jr. et a1. 102/702 G 3,106,161 10/1963 Wallbaum et a1 102/702 G 3,288,068 11/1966 Jefferson et al. 102/70.2 I 3,610,153 10/1971 Bctts 102/702 A 3,624,451 Gauld 102/702 A Primary ExaminerBenjamin A. Borchelt Assistant Examiner-C. T. Jordan Attorney, Agent, or FirmNathan Edelberg; Robert P. Gibson; Max Yarmovsky [57] ABSTRACT 5 Claims, 3 Drawing Figures J- LOOP 1 11:: I2

LOOP 2 U.S. Patent Oct.21, 1975 Sheet1of3 3,913,484

GE \um 55 L l n I :63 V 2 8 N 60 INVENTOR.

CARL J. GARDNER U.S. Patent Oct. 21, 1975 Sheet20f3 3,913,484

3 DET C LOOP 6 FIG 2 LOOP 2 LOOP1 INVENTOR.

CARL J. GARDNER BY! ELECTRONIC COUNTING FUZE The invention described herein may be manufactured, used and licensed by the Government for governmental purposes without payment to me of any royalty thereon.

BACKGROUND OF THE INVENTION The present invention relates to the field of art dealing with electronic fuzes for land mines.

The fuze herein disclosed possesses a capability long desired in land mines. Namely, rather than detonating upon a single pressure input, detonation can now be obtained after N pressure inputs. This capability imparts the present invention with potential effectiveness against columns of soldiers or vehicles. With N equal to a suitable number, e.g., 20, a mine equipped with the present fuze could detonate in the midst of a personnel or vehicle column.

SUMMARY OF THE INVENTION An object of this invention is to provide an electronic fuze for a land mine, said fuze being capable of initi at ing a detonation after a given number of pressure inputs.

Another object is to provide an anti-intrusion device having an alarm said alarm capable of initiating after a given number of pressure inputs.

The present electronic counting fuze comprises an electrical source unit providing an output only when subjected to pressure; a charge storage means, said storage means receiving a charge in pulse form from said electrical source unit upon each subjection of said source unit to pressure; and electronic gating means, said gating means connected intermediately between said storage means and a detonator, whereby said detonator will be activated after successive applications of pressure to said electrical source unit.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram of a crystal-powered counting fuze.

FIG. 2 is a circuit diagram of a transformer-coupled counting fuze.

FIG. 3 is a circuit diagram of a capacitor-bridge counting fuze.

DETAILED DESCRIPTION OF THE INVENTION One embodiment of the present invention is illustrated in FIG. 1 which shows a piezoelectric crystalpowered counting fuze. Said fuze is comprised of two circuit loops.

One loop comprises, in series relationship, a piezoelectric crystal pair 12, a resistor 14, a blocking diode l6 and a capacitor 18. Different values of the resistor 14 can be substituted. These alternate values of resistor 14 are denoted as resistors 15 in FIG. 1.

The second loop comprises said-capacitor 18 in parallel with the series combination of a gas diode and a resistor 22. Said resistor is in parallel with the detonator, denoted DET in FIG. I.

Said crystal-powered counting fuze operates as follows: The application of force by a potential target to the crystal 12 generates a voltage pulse across the resistor-capacitor combination of elements 14, and 18. When the force is relieved, a pulse of equal voltage and opposite polarity is generated. The blocking diode 16 prevents the capacitor 18 from becoming discharged by the reverse pulse. When a sufficient potential has been built up in capacitor 18 by several positive pulses from the crystal 12, the gas diode 20 will conduct a portion of the charge through the resistor 22. The voltage across resistor 22 will initiate the detonator.

Satisfactory results have been obtained with the following values of the components in FIG. 1: resistor 14, thousand ohms; capacitor 18, 0.1 microfarads; resistor 22, 10 thousand ohms.

The number of counts or input pulses needed to initiate the detonator can be changed by altering the value of resistor 14. This procedure, which is termed count selection, is accomplished by providing a group of different value resistors 15 for element 14.

It is to be noted that, as regards safety, since several counts would be needed for detonation, an accidental short of the detonator to the power source could not cause detonation.

The crystal-powered fuze, while enjoying the advantage of unlimited shelf life, is incapable of producing sufficient energy to initiate some higher energy detonators.

This problem was attacked through a second embodiment of the present invention which may be termed a transformer-coupled counting fuze. This fuze comprises six current loops. See FIG. 2. Loop 1 comprises in series relationship a battery 24, a sensor switch 26 such as a normally open pressure sensitive tape switch manufactured by Tapeswitch Corp. of America, 320 Broadhollow Rd., Farmingdale, N.Y., Model No. RBMA, or a normally open magnetic influence or proximity switch such as manufactured by Electro Products Laboratories, Inc., Chicago, Ill., Model No. 85,003, and a resistor 28. In the case of the pressure sensitive switch, the weight of troops and/or vehicles passing thereon is successively sensed. In the case of the magnetic influence switch, the presence or close proximity of magnetic material, such as vehicle frames or tank treads are being sensed. Loop 2 comprises in series relationship said resistor 28, a capacitor 30, and a transformer primary 31 of a transformer 32. Loop 3 comprises in series relationship a transformer secondary 33 of said transformer 32, a resistance 34, a blocking diode 36 and a capacitor 38. Loop 4 comprises in series relationship said capacitor 38, a gas diode 40 and a resistor 42. Loop 5 comprises the resistor 42 connected in parallel with two leads of a transistor 43: A base 44 of the transistor is connected between gas diode 40 and resistor 42. A collector 45 is connected between resistor 42 and capacitor 38. Loop 6 comprises in series relationship the base lead 44 of said transistor 43, an emitter 46 of said transistor, the detonator (denoted DET in FIG. 2), the switch 26, the capacitor 30, the transformer 32, the resistor 34, the blocking diode 36 and the gas diode 40. Count selection is obtained by providing a group of different valued resistors 35 which can be substituted for resistor 34.

The transformer-coupled counting fuze employs the same principle of capacitor storage and gas diode to resistor discharge as is used in the crystal-powered fuze. The input in FIG. 2 derives from switch closures, as from a button or a tape switch. With each closure of switch 26, the pulse from battery 24 is stepped up by transformer 32. When a sufficient charge builds up across capacitor 38 the gas diode 40 will discharge into resistor 42. The voltage pulse across resistor 42 acts as the input to transistor 43, which acts as a switch in initiating the detonator.

The capacitor coupling of elements 28 and 30 between the battery 24 and transformer 32 prevent damage to the battery in the event of a prolonged input switch closure.

Satisfactory results have been obtained with the following values of the components in FIG. 2: battery 24, 9 volts; resistor 28, 10 thousand ohms; capacitor 30, 100 microfarads; resistor 34, 100 thousand ohms; capacitor 38, one microfarad; and resistor 42, 100 ohms.

The need for a fuze with an output pulse of longer duration, a feature essential for initiation of certain detonators, led to the development ofa further modified design. This design is illustrated in FIG. 3 and is termed a capacitor-bridge counting fuze.

This fuze comprises seven circuit loops. See FIG. 3. Loop 1 comprises in series relationship a capacitor 47, one closure 48 of a double-pole single-throw arming switch 49, a second closure 50 of said double closure switch, and a battery 52. Loop 2 comprises in series relationship said battery 52, said second closure 50, a single-pole single-throw input switch 54 and a resistor 56. Loop 3 comprises in series relationship the resistor 56, a capacitor 58, and a first blocking diode 60. Capacitor 58 is provided with alternative capacitors 59 that can be switched into the circuit if a different number of counts isdesired for detonation. Loop 4 comprises in series relationship said first blocking diode 60, a second blocking diode 62 and a capacitor 64. Loop comprises in series relationship the capacitor 64, a Shockley diode 66 and a resistor 68. Loop 6 comprises the resistor 68 in parallel with two leads of a silicon control rectifier (SCR) 70. The trigger 71 of the SCR is connected between the Shockley diode 66 and the resistor 68. The cathode 72 is connected between the resistor 68 and the capacitor 64. Loop 7 comprises in series relationship trigger 71, anode 73 of the SCR 70, the detonator (denoted DET in FIG. 3), the single closure input switch 54, capacitor 58, second blocking diode 62, and the Shockley diode 66.

Closure of the input switch 54 after closure of switch 49, as by arming, causes a charge to be built up on the capacitor voltage divider formed by capacitors 58 and 64. During closure, resistor 56 is shorted across the battery 52, but the resistor 56 is large enough to prevent a serious drain on the battery during the time that the switch 54 remains closed. Within milliseconds of closure the voltage across capacitors 58 and 64 equals that of the battery. The voltage on capacitor 64 after pulses will equal E 1 [Cl/(C1+C2)] where E equals the voltage of the battery 52, Cl equals the capacitance of capacitor 64, and C2 equals the capacitance of capacitor 58. This formula is derived by open-circuit-short-circuit analysis.

Successive input pulses will cause voltage buildup on capacitor 64 as indicated in the above equation. When the voltage across this capacitor exceeds the breakover voltage of the Shockley diode 66, the capacitor discharges through the resistor 68, causing the SCR 70 to be forward biased. Since the detonator is in series with the SCR, the detonator will receive a pulse of about the voltage of battery 52 for as long as the battery is able to conduct.

Satisfactory results have been obtained with the following values for the elements illustrated in FIG. 3: ca-

pacitor 47, 100 microfarads; capacitor 58, 0.05 microfarads; capacitor 64, 0.2 microfarads; battery 52, 30

volts; resistor 56, 100 thousand ohms; and resistor 68,

2.7 thousand ohms.

5 It is to be noted that a magnetic influence switch can be readily substituted for sensor switch 26 or input switch 54. Certain combat environments would require such a switch.

A range of values for capacitor 58 incorporated into the design will provide users with a capability of selecting the number of counts needed to detonate a mine. Switch 49 is the safe and arm switch which isolates the battery from the circuit during storage to prevent both premature detonation and drainage of the battery. Capacitor 47 provides a low impedance energy source to fire the detonator; its leakage resistance (about 5 X ohms) will not cause a serious drain on the battery during normal shelf life. To prevent the SCR 70 from triggering accidentally when the switch 49 is moved to the armed position, it may be necessary to place the small capacitor in parallel with the SCR.

Three alternate methods are suggested for modifying the counter so that it will automatically reset itself if input pulses are too infrequent:

a. Using a controlled leakage resistance capacitor such as capacitor 64,

b. Using diodes 60 and 62 with specified reverse leakage currents, and

c. Adding a large resistance in parallel with capacitor The proper selection of these components will depend on the users requirements. The selection of a power source depends on its shelf life and temperature sensitivity. Various available power sources with shelf lives of 2 to 4 years would be suitable for a system in which the battery is changeable. For a system where the battery is to be potted in the same package as the counter, a longer life is necessary. At present, one source is available, a solid-ion type battery, which has a l0-year shelf life and can withstand high temperature environments.

Also, it should be noted that the present-invention could easily be microminiaturized and constructed on a chip.

Finally, cognizance should be taken of the fact that by means of a substitution of an alarm for the detonator, an effective anti-intrusion device is obtained.

It is thus seen that the objects set forth above are among those made apparent from, and efficiently attained by, the preceding description.

I wish it to be understood that I do not desire to be limited to the exact detail of construction shown and described for obvious modification will occur to persons skilled in the art.

What I claim and desire to be secured by Letters Patent of the United States is:

l. A counting fuze for a land mine having a detonator, comprising:

an electrical source unit providing an output only when subject to pressure which includes:

a pressure-sensitive switching means; and

a source of electrical power, said source connected to said switching means, said source of electrical power activated and inactivated by respective closings and openings of said pressure-sensitive switching means;

a charge storage means, said storage means receiving a charge in pulse form from said electrical source unit upon each subjection of said source unit to pressure; and

electronic gating means, said gating means being connected intermediately between said storage means and said detonator, whereby said detonator will be activated after successive applications of pressure to said electrical source unit.

2. The counting fuze of claim 1 wherein said pressure-sensitive switching means comprises a tape switch.

3. An electrical counting fuze for a land mine having a detonator comprising three circuit loops,

one loop comprising in series connected relationship, piezoelectric crystals, a first resistor, a blocking diode and capacitor;

a second loop comprising in series connected relationship, said capacitor, a gas diode, and a second resistor;

a third loop comprising said second resistor connected in parallel with said detonator.

4. An electrical counting fuze for a land mine having a detonator, comprising six circuit loops,

a first loop comprising in series connected relationship, a battery, a pressure-sensitive switch, and a first resistor;

a second loop comprising in series connected relationship, said first resistor, a first capacitor, and a transformer primary of a transformer;

a third loop comprising in series connected relationship, a transformer secondary of said transformer, a second resistance, a blocking diode and a second capacitor;

a fourth loop comprising in series connected relationship, said second capacitor, a gas diode, and a third resistor;

a fifth loop comprising in series connected relationship, said third resistor, a collector of a transistor and a base of said transistor; and

a sixth loop comprising in series connectedrelationship, said base of said transistor, an emitter of said transistor, said detonator, said pressure-sensitive switch, said first capacitor, said transformer, said second resistor, said blocking diode and said gas diode.

5. An electricalcounting fuze, for a land mine having 10 a detonator comprising seven circuit loops.

a first loop comprising in series connected relationship, a first capacitor, one closure of a double-pole single-throw switch, a second closure of said double-pole single-throw switch, and a battery;

a second loop comprising in series connected relationship, said battery, said second closure, a singlepole single-throw switch and a first resistor;

a third loop comprising in series connected relationship, said first resistor, a second capacitor, and a first blocking diode;

a fourth loop comprising in series connected relationship, said first blocking diode, a second blocking diode and a third capacitor;

a fifth loop comprising in series connected relationship, said third capacitor, a Shockley diode, and a second resistor;

a sixth loop comprising in series connected relationship, said second resistor, a trigger of a silicon control rectifier, and a cathode of said silicon control rectifier; and

a seventh lead loop comprising in series connected relationship, said trigger, an anode of said SCR, said detonator, said single-pole single-throw switch, said second capacitor, said second blocking diode, and said Shockley diode. 

1. A counting fuze for a land mine having a detonator, comprising: an electrical source unit providing an output only when subject to pressure which includes: a pressure-sensitive switching means; and a source of electrical power, said source connected to said switching means, said source of electrical power activated and inactivated by respective closings and openings of said pressure-sensitive switching means; a charge storage means, said storage means receiving a charge in pulse form from said electrical source unit upon each subjection of said source unit to pressure; and electronic gating means, said gating means being connected intermediately between said storage means and said detonator, whereby said detonator will be activated after successive applications of pressure to said electrical source unit.
 2. The counting fuze of claim 1 wherein said pressure-sensitive switching means comprises a tape switch.
 3. An electrical counting fuze for a land mine having a detonator comprising three circuit loops, one loop comprising in series connected relationship, piezoelectric crystals, a first resistor, a blocking diode and capacitor; a second loop comprising in series connected relationship, said capacitor, a gas diode, and a second resistor; a third loop comprising said second resistor connected in parallel with said detonator.
 4. An electrical counting fuze for a land mine having a detonator, comprising six circuit loops, a first loop comprising in series connected relationship, a battery, a pressure-sensitive switch, and a first resistor; a second loop comprising in series connected relationship, said first resistor, a first capacitor, and a transformer primary of a transformer; a third loop comprising in series connected relationship, a transformer secondary of said transformer, a sEcond resistance, a blocking diode and a second capacitor; a fourth loop comprising in series connected relationship, said second capacitor, a gas diode, and a third resistor; a fifth loop comprising in series connected relationship, said third resistor, a collector of a transistor and a base of said transistor; and a sixth loop comprising in series connected relationship, said base of said transistor, an emitter of said transistor, said detonator, said pressure-sensitive switch, said first capacitor, said transformer, said second resistor, said blocking diode and said gas diode.
 5. An electrical counting fuze, for a land mine having a detonator comprising seven circuit loops. a first loop comprising in series connected relationship, a first capacitor, one closure of a double-pole single-throw switch, a second closure of said double-pole single-throw switch, and a battery; a second loop comprising in series connected relationship, said battery, said second closure, a single-pole single-throw switch and a first resistor; a third loop comprising in series connected relationship, said first resistor, a second capacitor, and a first blocking diode; a fourth loop comprising in series connected relationship, said first blocking diode, a second blocking diode and a third capacitor; a fifth loop comprising in series connected relationship, said third capacitor, a Shockley diode, and a second resistor; a sixth loop comprising in series connected relationship, said second resistor, a trigger of a silicon control rectifier, and a cathode of said silicon control rectifier; and a seventh lead loop comprising in series connected relationship, said trigger, an anode of said SCR, said detonator, said single-pole single-throw switch, said second capacitor, said second blocking diode, and said Shockley diode. 